[dba-VB] c# lock()

John --

Let's define your target (application) system architecture on conceptual
level - I guess that using "micro-level locking" you're trying (?) to
achieve isn't needed...

1) you have a huge input data set;
2) you split input data set into X chunks;
3) every chunk gets processed using the same several - Y - steps;
4) on completion of step Yn input/semi-processed chunk Xn is submitted to
the Y(n+1) processor class;
5) when all X chunks are processed in Y steps they get collected into a
final "huge" output set to produce Z reports.

That's it from conceptual high level point of view?
Something important missing?
Too simplified to be true?

John, please take into account that I can't reply promptly here - it's
weekend now and I'll be out tomorrow, and it's 1:26 a.m. - time to sleep,
and then I have quite some work to do starting Monday - so I expect this
thread will be supported by other AccessD/dba-VB members...

Thank you.

--
Shamil
 
-----Original Message-----
From: dba-vb-bounces at databaseadvisors.com
[mailto:dba-vb-bounces at databaseadvisors.com] On Behalf Of jwcolby
Sent: 27 ????? 2011 ?. 0:53
To: Discussion concerning Visual Basic and related programming issues.
Subject: Re: [dba-VB] c# lock()

Shamil,

I am trying to build a base class which contains a set of lock objects and
some standard variables. 
  Having defined the lock objects static per your code below, the derived
class cannot access the lock objects even though I set them protected:

protected static Object LockBln = new Object();

In the derived class when I try to access it:

lock(this.LockBln)
{
}

I get a compile error:

"Member cannot be accesses with an instance reference; Qualify it with a
type name instead."

What does this mean?

Reading on the internet it says that static properties are shared between
all instances of the class.  I don't see how I can share a property between
50 instances and then use a
lock(MyStaticProperty) {}.

I'm so confused...

John W. Colby
www.ColbyConsulting.com

On 3/25/2011 5:05 PM, Shamil Salakhetdinov wrote:
> Hi John --
>
> Your sample is a correct usage of locking - just use static thisLock 
> variable
>
> private static Object thisLock = new Object()
>
> as non-static variable *is not* thread safe AFAIU.
>
> Yes, such locking can be done for various operations of that class - 
> just make sure you'll not get dead-locked...
> Also use *one lock object* to lock *one resource* in a class - 
> otherwise "deadlock" will become your "everyday guest"...
>
> Thank you.
>
> --
> Shamil
>
> -----Original Message-----
> From: dba-vb-bounces at databaseadvisors.com
> [mailto:dba-vb-bounces at databaseadvisors.com] On Behalf Of jwcolby
> Sent: 25 ????? 2011 ?. 22:58
> To: Discussion concerning Visual Basic and related programming issues.
> Subject: Re: [dba-VB] c# lock()
>
> Shamil,
>
> Does this allow using a single "lock object" to lock various 
> operations in a class.
>
> For example I want to lock a date flag variable while using a property 
> to either get or set the variable.
>
>           private Object thisLock = new Object();
>
>           public DateTime pFlagDte {
>               get {
>                   lock (thisLock)
>                   {
>                       return dteFlag;
>                   }
>               }
>               set
>               {
>                   lock (thisLock)
>                   {
>                       dteFlag = value;
>                   }
>               }
>           }
>
> The issue is not multiple threads trying to write to the date variable 
> but rather one thread trying to read it while another is writing it.
>
> John W. Colby
> www.ColbyConsulting.com
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